Metering pump device

ABSTRACT

A metering pump device capable of performing a fixed amount of discharge with a high accuracy even if a pressure difference occurs between outflow side valves. In the metering pump device, two reciprocating pump devices are used. The end and start of the discharge period of one reciprocating pump device are overlapped with the start and end of the discharge period of the other reciprocating pump device. After the inhalation operation and before the discharge period, both the inflow side valves and the outflow side valves are closed to perform a correction operation for eliminating the pressure difference by increasing or decreasing the internal volumes of the pump chambers.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a U.S. national stage application of PCT International application No. PCT/JP2007/058484, filed on Apr. 19, 2007. Priority under 35 U.S.C. §119(a) and 35 U.S.C. §365(b) is claimed from Japanese Application No. 2006-117194, filed Apr. 20, 2006, the disclosures of which are also incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a metering pump device which is provided with a plurality of reciprocating pump devices.

BACKGROUND

There is a metering pump device which utilizes a reciprocating pump device. In a reciprocating pump, there always exists a point where a discharge amount becomes zero at a top dead point or a bottom dead point and thus accuracy of a constant-quantity discharge is not satisfactory. Therefore, a structure has been proposed in which two reciprocating pump devices are connected in parallel to each other and, at the time when discharge of one of the reciprocating pump devices has finished, the other of the reciprocating pump devices starts to discharge so that the whole discharge flow rate becomes constant (see Patent Reference 1).

[Patent Reference 1] Japanese Patent Laid-Open No. 2001-207951.

SUMMARY

However, even when two reciprocating pump devices are phased each other like reciprocating pump devices disclosed in Patent Reference 1, in a case when there is a difference in pressure between an inside of a pump chamber and a common discharge port side, immediately after an outflow side valve has been changed to an open state, outflow of fluid from the pump chamber to the common discharge port side may occur, or inflow of fluid from the common discharge port side to the inside of the pump chamber may occur, which incurs a problem that discharge amount is varied. In the metering pump device disclosed in Patent Reference 1, an inflow side valve is set in an open state to contract the pump chamber in order to discharge air bubbles from the pump chamber after fluid is sucked into the pump chamber. However, in this operation, dispersion of discharge amount per unit of time cannot be prevented when there is a difference in pressure between the inside of the pump chamber and the common discharge port side.

In view of the problems described above,the present invention may provide a metering pump device which is capable of discharging quantitatively or discharging at a constant rate with a high degree of accuracy even when a difference in pressure is generated on both sides of an outflow side valve.

In order to achieve the above, there may be provided a metering pump device including a plurality of reciprocating pump devices each of which is connected with an inflow side valve and an outflow side valve on an inflow side and an outflow side, a common discharge port which is connected with the plurality of the reciprocating pump devices through the outflow side valves, and a control part for controlling the inflow side valves, the outflow side valves and the reciprocating pump devices. The control part sets a discharge period and a waiting period for each of the plurality of the reciprocating pump devices so as to shift timings of the discharge period and the waiting period each other, and a starting time and an ending time of the discharge period of one of the reciprocating pump devices are superposed on an ending time and a starting time of the discharge period of another reciprocating pump device and, after a suction operation into a pump chamber has been performed in the waiting period and before the discharge period, a correcting operation is performed in which both of the inflow side valve and the outflow side valve are closed and a volume within the pump chamber is expanded or contracted to eliminate a difference in pressure between a pressure within the pump chamber and a common discharge port side.

According to at least an embodiment of the present invention, a plurality of reciprocating pump devices is used and a starting time and an ending time of the discharge period of one of the reciprocating pump devices are superposed on an ending time and a starting time of the discharge period of another reciprocating pump device. Therefore, even when there is a point where a discharge amount becomes zero at a top dead point or a bottom dead point in the reciprocating pump device, the entire amount of discharge flow becomes always constant. Further, after a suction operation and before a discharge period, a correcting operation is performed in which both of the inflow side valve and the outflow side valve are closed and a volume within the pump chamber is expanded or contracted to eliminate a difference in pressure. Therefore, even when there is a difference in pressure on both sides of the outflow side valve, discharging quantitatively or discharging at a constant rate can be performed with a high degree of accuracy.

In accordance with at least an embodiment of the present invention, a plurality of reciprocating pump devices may be structured so that they are connected to separate suction ports through separate inflow side valves. However, a structure may be used in which a common suction port is connected with the plurality of the reciprocating pump devices through the inflow side valves.

In at least an embodiment of the present invention, it is preferable that a drive source for the reciprocating pump device is a stepping motor or an AC synchronous motor. In such a motor, even when energization is stopped, position holding for the rotor can be attained by holding power. Therefore, even when position holding for a valve element is to be performed, continuous energization is not required which is different from a case where a solenoid or the like is used, and thus power consumption can be reduced. Further, when a drive source for the reciprocating pump device is a stepping motor, it is preferable that a variation amount of an internal volume of the pump chamber corresponding to one (1) step of the stepping motor is set to be 1/100 or less with respect to an entire internal volume of the pump chamber. According to this structure, a metering pump device with a high degree of resolving power can be realized.

In at least an embodiment of the present invention, a structure may be used in which a monitoring device is provided for directly or indirectly monitoring a difference in pressure between a pressure in an inside of the pump chamber in the reciprocating pump device and a pressure on the common discharge port side, and the control part performs the correcting operation on a basis of a monitoring result in the monitoring device when there is a difference in pressure between a pressure in the inside of the pump chamber and the pressure on the common discharge port side.

In at least an embodiment of the present invention, a structure may be used in which the monitoring device is provided with a plurality of first pressure sensors for monitoring respective pressures within the pump chambers of the plurality of the reciprocating pump devices, and a second pressure sensor for monitoring a pressure on the common discharge port side, and the difference in pressure is monitored by comparing a detection result of the first pressure sensor with a detection result of the second pressure sensor.

In at least an embodiment of the present invention, a structure may be used in which the monitoring device is provided with a plurality of pressure sensors for monitoring respective pressures within the pump chambers of the plurality of the reciprocating pump devices, and the difference in pressure is monitored by comparing a detection result of a pressure sensor, which is disposed in the pump chamber of the reciprocating pump device in which the suction operation is performed, with a detection result of a pressure sensor which is disposed in the pump chamber of the reciprocating pump device whose output side valve is opened.

Thus, a metering pump device, which is capable of realizing the above-mentioned control, may be provided with a plurality of reciprocating pump devices each of which is connected with an inflow side valve and an outflow side valve on an inflow side and an outflow side, a common discharge port which is connected with the plurality of the reciprocating pump devices through the outflow side valves, and pressure sensors for monitoring respective pressures within the pump chamber of the plurality of the reciprocating pump devices.

In at least an embodiment of the present invention, when a number of the reciprocating pump device is two, the control device may set an expanding speed of the pump chamber at the time of the suction operation higher than a contracting speed of the pump chamber in the discharge period.

In the metering pump device in accordance with at least an embodiment of the present invention, a plurality of reciprocating pump devices is used and a starting time and an ending time of the discharge period of one of the reciprocating pump devices are superposed on an ending time and a starting time of the discharge period of another reciprocating pump device. Therefore, even when there is a point where a discharge amount becomes zero at a top dead point or a bottom dead point in the reciprocating pump device, the entire amount of discharge flow becomes always constant. Further, after a suction operation and before a discharge period, a correcting operation is performed in which both of the inflow side valve and the outflow side valve are closed and a volume within the pump chamber is expanded or contracted to eliminate a difference in pressure. Therefore, when there is a difference in pressure between an inflow side of an inflow side valve and a discharge side of a discharge side valve, as a result, even when there is a difference in pressure on both sides of the outflow side valve, discharging quantitatively or discharging at a constant rate can be performed with a high degree of accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described, by way of example only, with reference to the accompanying drawings which are meant to be exemplary, not limiting, and wherein like elements are numbered alike in several Figures, in which:

FIG. 1 is a schematic view showing a basic structure of a metering pump device in accordance with a first embodiment of the present invention.

FIG. 2 is a perspective view showing a structural example of the metering pump device shown in FIG. 1.

FIG. 3 is a longitudinal sectional view showing a main body portion of the metering pump device shown in FIG. 2.

FIGS. 4( a) through 4(h) are timing charts showing an operation of a metering pump device to which at least an embodiment of the present invention is applied.

FIGS. 5( a) through 5(h) are timing charts showing an operation of a metering pump device to which at least an embodiment of the present invention is applied.

FIG. 6 is a schematic view showing a basic structure of a metering pump device in accordance with a second embodiment of the present invention.

FIG. 7 is a schematic view showing a basic structure of a metering pump device in accordance with a third embodiment of the present invention.

FIG. 8 is an exploded perspective view showing a reciprocating pump device which is longitudinally divided and is used in a metering pump device to which at least an embodiment of the present invention is applied.

FIG. 9 is an explanatory longitudinal sectional view showing an active valve which is used as an inflow side valve and an outflow side valve in a metering pump device to which at least an embodiment of the present invention is applied.

FIG. 10 is an explanatory longitudinal sectional view showing another active valve which is viewed from obliquely above and is used as an inflow side valve and an outflow side valve in a metering pump device to which at least an embodiment of the present invention is applied.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Embodiments of the present invention will be described below with reference to the accompanying drawings.

First Embodiment (Device Structure)

FIG. 1 is a schematic view showing a basic structure of a metering pump device to which at least an embodiment of the present invention is applied. FIG. 2 is a perspective view showing a structural example of a metering pump device to which at least an embodiment of the present invention is applied. FIG. 3 is a longitudinal sectional view showing a main body portion of the metering pump device shown in FIG. 2.

As shown in FIG. 1, a metering pump device 1 in this embodiment is a pump device for discharging liquid or gas quantitatively or at a constant rate. The metering pump device 1 is provided with two reciprocating pump devices 10A and 10B in which inflow side valves 11Ai and 11Bi and outflow side valves 11Ao and 11Bo are respectively connected to inflow passages 12Ai and 12Bi and outflow passages 12Ao and 12Bo. A common discharge port 13 o is structured in a common outflow passage 12 o which is connected to the two reciprocating pump devices 10A and 10B through the outflow side valves 11Ao and 11Bo. Further, in the metering pump device 1 in this embodiment, a common suction port 13 i is structured in a common inflow passage 12 i which is connected to the two reciprocating pump devices 10A and 10B through the inflow side valves 11Ai and 11Bi. In this embodiment, the reciprocating pump devices 10A and 10B are provided with the same structure as each other and all of the inflow side valves 11Ai and 11Bi and the outflow side valves 11Ao and 11Bo are provided with the same structure as each other. Further, the inflow passages 12Ai and 12Bi are provided with the same structure as each other and the outflow passages 12Ao and 12Bo are provided with the same structure as each other.

The metering pump device 1 in this embodiment is, for example, as shown in FIG. 2, provided with a main body portion 2 in a rectangular parallelepiped shape in which plural pieces of plate are laminated and a control device 3 (control part) which is connected with the main body portion 2 through a connector and a cable. The main body portion 2 is structured so that a bottom plate 75, a base plate 76, a flow passage structure plate 77, and a top plate 78 for closing an upper face of the flow passage by covering an upper face of the flow passage structure plate 77 are laminated in this order. A pipe 781 structuring the common discharge port 13 o and a pipe 782 structuring the common suction port 13 i are connected to the top plate 78.

As shown in FIG. 3, each of the reciprocating pump devices 10A and 10B is provided with a valve element comprised of a diaphragm valve 170, which is disposed in a pump chamber 20, and a drive device 105 including a stepping motor (drive source) for driving the valve element to contract or expand an internal volume of the pump chamber 20. When the stepping motor is rotated in one direction, the diaphragm valve 170 is driven in a direction to expand the internal volume of the pump chamber 20 and, when the stepping motor is rotated in the opposite direction, the diaphragm valve 170 is driven in the direction where the internal volume of the pump chamber 20 is contracted. In this embodiment, an amount of change of the internal volume of the pump chamber 20 corresponding to one step of the stepping motor is set to be 1/100 or less to the entire internal volume of the pump chamber 20.

The inflow side valves 11Ai and 11Bi and the outflow side valves 11Ao and 11Bo are respectively an active valve which is provided with a valve element (diaphragm valve 260) and a linear actuator 201 and they perform an opening/closing operation independently.

(Operation)

FIGS. 4( a)-4(h) are timing charts showing an operation of a metering pump device in this embodiment and its control is performed by the control device 3 shown in FIG. 2.

FIG. 4( a) shows a state where a valve element is driven by a stepping motor in the first reciprocating pump device 10A. In FIG. 4( a), an upward period in the waveform shows a state where the pump chamber 20 is contracted to discharge fluid and a downward period in the waveform shows a state where the pump chamber 20 is expanded to suck liquid. FIGS. 4( b) and 4(c) show states where the inflow side valve 11Ai and the outflow side valve 11Ao are driven for the first reciprocating pump device 10A. When an upward signal in the waveform is inputted, after that, the valve is maintained in an open state until a downward signal in the waveform is inputted. When a downward signal in the waveform is inputted, after that, the valve is maintained in a close state until an upward signal in the waveform is inputted. FIG. 4( d) shows a state where a valve element is driven by a stepping motor in the second reciprocating pump device 10B. In FIG. 4( d), during an upward period in the waveform, the pump chamber 20 is contracted to discharge liquid and, during a downward period in the waveform, the pump chamber 20 is expanded to suck liquid. FIGS. 4( e) and 4(f) show states where the inflow side valve 11Bi and the outflow side valve 11Bo are driven for the second reciprocating pump device 10B. When an upward signal in the waveform is inputted, after that, the valve is maintained in an open state until a downward signal in the waveform is inputted. When a downward signal in the waveform is inputted, after that, the valve is maintained in a close state until an upward signal in the waveform is inputted. FIG. 4( g) shows a synthesized result of discharge amounts of liquids (discharge amount from the common discharge port 13 o) which are discharged from the first reciprocating pump device 10A and the second reciprocating pump device 10B. FIG. 4( h) shows a synthesized result of suction amounts of liquids (suction amount from the common suction port 13 i) which are sucked into the first reciprocating pump device 10A and the second reciprocating pump device 10B.

Although an operation for each time will be described below, in this embodiment, as shown in an upper side of FIGS. 4( a)-4(h), the control device 3 sets discharge periods T1A and T1B and waiting periods T2A and T2B at shifted timings for two reciprocating pump devices 10A and 10B. In addition, a starting time and an ending time of a discharge period (for example, discharge period T1A) of one of the reciprocating pump devices (for example, the first reciprocating pump device 10A) are superposed on an ending time and a starting time of a discharge period (for example, discharge period T1B) of the other of the reciprocating pump devices (for example, the second reciprocating pump device 10B).

Further, after a suction operation to the pump chamber 20 has been performed during the waiting periods T2A and T2B and, before the discharge periods T1A and T1B, the control device 3 performs a correcting operation in which both the inflow side valves 11Ai and 11Bi and the outflow side valves 11Ao and 11Bo are set in close states and a volume within the pump chamber 20 is contracted to eliminate a difference in pressure.

In FIGS. 4( a)-4(h), first, up to the time “t0”, the reciprocating pump devices 10A and 10B are in a stop state in which liquid (fluid) has been sucked to the respective pump chambers 20. Further, all of the valves are in a close state. In this state, as shown in FIGS. 4( a), 4(b) and 4(c), after the outflow side valve 11Ao for the first reciprocating pump device 10A is opened at the time “t0”, at the time “t1”, the valve element in the first reciprocating pump device 10A is driven in a direction so that the pump chamber 20 is contracted and, as a result, a liquid discharge is started. This discharge continues during the discharge period T1A (i.e., from time “t1” up to the time “t8”) and, during this time period, the first reciprocating pump device 10A discharges liquid in a fixed quantity.

Then, at the time “t8”, the outflow side valve 11Ao for the first reciprocating pump device 10A is set in a close state and the liquid discharge is stopped. This stopped state is continued during the waiting period T2A up to the time “t13”. In this waiting period T2A, at the time “t9”, the inflow side valve 11Ai for the first reciprocating pump device 10A is set in an open state and, after that, from the time “t10” to the time “t11”, the valve element in the first reciprocating pump device 10A is driven in a direction to expand the pump chamber 20 to perform a suction operation of liquid.

Next, at the time “t13”, the outflow side valve 11Ao for the first reciprocating pump device 10A is set in an open state again and, after that, at the time “t14”, the valve element in the first reciprocating pump device 10A is driven in a direction to contract the pump chamber 20 again and liquid discharge is started. This discharge is continued during the discharge period T1A up to the time “t22” and, during that time period, the first reciprocating pump device 10A discharges liquid at a constant rate.

At the time “t22”, the outflow side valve 11Ao for the first reciprocating pump device 10A is set in the close state and the liquid discharge is stopped. This stop state is continued during the waiting period T2A (i.e., from time “t22” up to the time “t27”). In this waiting period T2A, at the time “t23”, the inflow side valve 11Ai for the first reciprocating pump device 10A is set in the open state and, after that, from the time “t24” to the time “t25”, the valve element in the first reciprocating pump device 10A is driven in a direction to expand the pump chamber 20 and a liquid suction operation is performed. Afterwards, the above-mentioned serial operations are repeated with the valve element in the first reciprocating pump device 10A driven in a direction between time “t28” through “t29” to contract the pump chamber 20 again and liquid discharge started again.

On the other hand, as shown in FIGS. 4( d), 4(e) and 4(f), the same operations are performed in the second reciprocating pump device 10B but their timings are shifted. Therefore, at the time “t6”, the outflow side valve 11Bo for the second reciprocating pump device 10B is set in an open state and, after that, at the time “t7”, the valve element in the second reciprocating pump device 10B is driven in a direction to contract the pump chamber 20 and a liquid discharge is started. The discharge is continued during the discharge period “T1B” up to the time “t15” and, during that time period, the second reciprocating pump device 10B discharges the liquid at a constant rate. Next, at the time “t15”, the outflow side valve 11Bo for the second reciprocating pump device 10B is set in a close state and the liquid discharge is stopped. This stop state is continued during the waiting period T2B up to the time “t20”. In the waiting period T2B, at the time “t16”, the inflow side valve 11Bi for the second reciprocating pump device 10B is set in an open state and, after that, from the time “t17” to the time “t18”, the valve element in the second reciprocating pump device 10B is driven in a direction to expand the pump chamber 20 and a liquid suction operation is performed. Afterwards, the above-mentioned serial operations are repeated.

In this embodiment, in the time period “t7” through “t8” and the time period “t21” through “t22”, the ending time of the discharge period T1A of the first reciprocating pump device 10A is overlapped with the starting time of the discharge period T1B of the second reciprocating pump device 10B. Further, in the time period “t14” through “t15”, the ending time of the discharge period T1B of the second reciprocating pump device 10B is overlapped with the starting time of the discharge period T1A of the first reciprocating pump device 10A. Therefore, as shown in FIG. 4( h), liquid suction is intermittently performed but, as shown in FIG. 4( g), a discharge rate (discharge amount per unit time) is always constant which is a synthesized liquid discharge amount (discharge amount from a common discharge port), which is synthesized of amounts that are discharged from the first reciprocating pump device 10A and the second reciprocating pump device 10B.

(Correcting Operation for Pressure Difference)

In the metering pump device 1 in this embodiment, in a case that there is a difference in pressure between the inside of the pump chamber 20 and the common discharge port 13 o side, immediately after the outflow side valves 11Ao and 11Bo have been changed into the open state, outflow of liquid occurs from the pump chamber 20 to the common discharge port 13 o side or inflow of liquid occurs from the common discharge port 13 o side to the pump chamber 20 to vary the discharge amount.

In order to prevent this problem, in this embodiment, conditions are set in the control device 3 based on operating conditions of the metering pump device 1 so that a pressure in the common discharge port 13 o side is higher than a pressure within the pump chamber 20. In other words, the control device 3 performs a correcting operation according to a previously set condition such that, in the waiting periods T2A and T2B, after a suction operation to the pump chamber 20 has been performed and before the discharge periods T1A and T1B, during the time periods “t5” through “t6”, “t12” through “t13” and “t19” through “t20”, both of the inflow side valve 11Ai and the outflow side valve 11Ao are closed, or both of the inflow side valve 11Bi and the outflow side valve 11Bo are closed, the valve element is driven in a direction contracting a volume of the inside of the pump chamber 20 in the first reciprocating pump device 10A or the second reciprocating pump device 10B. For example, in the waiting period T2A, after a suction operation to the pump chamber 20 has been performed and before the discharge period T1A, during the time periods “t5” through “t6” and “t19” through “t20”, both of the inflow side valve 11Ai and the outflow side valve 11Ao for the first reciprocating pump device 10A are closed and the valve element is driven in a direction contracting the volume of the inside of the pump chamber 20 in the first reciprocating pump device 10A to increase a pressure in the pump chamber 20 to eliminate a difference in pressure with respect to the common discharge port 13 o side. Further, in the waiting period T2B, after a suction operation to the pump chamber 20 has been performed and before the discharge period T1B, during the time period “t12” through “t13”, both of the inflow side valve 11Bi and the outflow side valve 11Bo for the second reciprocating pump device 10B are closed and the valve element is driven in a direction contracting the volume of the inside of the pump chamber 20 of the second reciprocating pump device 10B to increase a pressure in the pump chamber 20 to eliminate a difference in pressure with respect to the common discharge port 13 o side.

In the embodiment described above, since the pressure on the common discharge port 13 o side is higher than the pressure in the inside of the pump chamber 20, the pressure within the pump chamber 20 before being discharged is increased. However, in a case that a pressure on the common discharge port 13 o side is lower than a pressure in the inside of the pump chamber 20, as shown in FIGS. 5( a)-5(h), a correcting operation may be performed in which, in the waiting periods T2A and T2B, after a suction operation to the pump chamber 20 has been performed and before the discharge periods T1A and T1B, during the time periods “t5” through “t6”, “t12” through “t13” and “t19” through “t20”, both of the inflow side valve and the outflow side valve are closed and a valve element is driven in a direction expanding a volume in the inside of the pump chamber 20.

(Principal Effects of this Embodiment)

As described above, in the metering pump device 1 in this embodiment, two reciprocating pump devices 10A and 10B are used and a starting time and an ending time of a discharge time period of one of the reciprocating pump devices are overlapped with an ending time and a starting time of a discharge time period of the other of the reciprocating pump devices. Therefore, in the reciprocating pump devices 10A and 10B, even when a discharge amount becomes zero at a top dead point or a bottom dead point, the entire discharge flow rate becomes always constant.

Further, after the suction operation and before the discharge periods T1A and T1B, the correcting operations T3A and T3B are performed in which both of the inflow side valve and the outflow side valve are closed and the volume of the inside of the pump chamber 20 is expanded or contracted to eliminate a difference in pressure. Therefore, even when there is a difference in pressure on both sides of the outflow side valves 11Ao and 11Bo, discharging at a constant rate can be performed with a high degree of accuracy. Further, in a case that a diaphragm valve is used as a valve element, unnecessary deformation may occur in the diaphragm valve due to a difference in pressure between an internal-pressure of the pump chamber 20 and atmospheric pressure. However, in this embodiment, suction and discharge can be performed while the above-mentioned deformation is corrected and thus high degree of accuracy for suction amount and discharge amount is obtained.

Further, in the reciprocating pump devices 10A and 10B, an operation is controlled by a signal pattern which is supplied to a stepping motor used in the drive device 105. Therefore, different from a structure in which an operation of a reciprocating pump device is controlled by a cam mechanism, a moving speed of a valve element (diaphragm valve 170) can be easily changed only by changing a signal pattern which is supplied to the stepping motor. Accordingly, the reciprocating pump devices 10A and 10B can stably deal with a condition from a little discharge amount to a large discharge amount per unit time. Further, even in a case of condition that a discharge amount per unit time is large, reciprocating number of times of the diaphragm valve 170 is small and thus service life time of the metering pump device 1 is increased.

Further, each of the inflow side valves 11Ai and 11Bi and the outflow side valves 11Ao and 11Bo is an active valve which independently performs an opening/closing operation and thus both of the inflow side and the outflow side can be prevented from being opened. Therefore, even when a pressure in the valve suction port 13 i side is higher than that in the discharge opening 13 o side, a forward flow does not occur and thus the metering pump device 1 is capable of discharging at a constant rate all the time. Further, when all of the inflow side valves 11Ai and 11Bi and the outflow side valves 11Ao and 11Bo are set in the open state and the reciprocating pump devices 10A and 10B are operated, liquid can be drawn from the insides of the reciprocating pump devices 10A and 10B. As a result, freeze proofing can be easily performed.

In addition, in the metering pump device 1 in this embodiment, the suction side and the discharge side are provided with the same structure and thus the suction side and the discharge side can be replaced with each other to be operated. Therefore, liquid recovery can be performed from the discharge side to the suction side.

In addition, a stepping motor is used as a drive source in the drive device 105 of the reciprocating pump devices 10A and 10B and a variation amount of the internal volume of the pump chamber 20 corresponding to one (1) step of the stepping motor is set to be 1/100 or less with respect to the entire internal volume of the pump chamber 20. Therefore, the resolving power of the metering pump device 1 in this embodiment is high. Further, when energization is stopped, a stepping motor can hold the position of the rotor by holding power. Therefore, even when a position holding of the diaphragm valve 170 is performed, continuous energization is not required which is different from a case when a solenoid or the like is used and thus low power consumption can be attained. According to this viewpoint, an AC synchronous motor may be used instead of the stepping motor.

Second Embodiment

In the first embodiment, it is set in advance that the correcting operations shown in FIG. 4 or 5 are performed. However, in the second embodiment, a monitoring device is provided which directly or indirectly monitors a difference in pressure between pressures in the insides of the pump chambers 20 in the reciprocating pump devices 10A and 10B and that of the common discharge port 13 o side. The control device 3 performs a correcting operation which is described with reference to FIGS. 4( a)-4(h) or FIGS. 5( a)-5(h) on the basis of a monitoring result in the monitoring device when there is a difference in pressure between a pressure in the inside of the pump chamber 20 and the common discharge port side.

In this embodiment, as shown in FIG. 6, first pressure sensors 14A and 14B which monitor pressures in the respective pump chambers 20 in the reciprocating pump devices 10A and 10B and a second pressure sensor 14o which monitors a pressure in the common discharge port 13 o side are used as the monitoring device. In the monitoring device structured as described above, for example, after a suction operation to the inside of the pump chamber 20 has finished, detection results of the first pressure sensors 14A and 14B and a detection result of the second pressure sensor 14 o are compared with each other and a difference in pressure is monitored. The control device 3 determines on the basis of the monitoring result which condition of the correcting operations is performed, in other words, which condition is performed whether the condition shown in FIGS. 4( a)-4(h) or the condition shown in FIGS. 5( a)-5(h). On the other hand, when there is no difference in pressure between the inside of the pump chamber 20 and the common discharge port side, the correcting operation is not performed.

Third Embodiment

In the first embodiment, it is set in advance that the correcting operations shown in FIG. 4 or 5 are performed. However, in the third embodiment, similarly to the second embodiment, a monitoring device is provided which directly or indirectly monitors a difference in pressure between pressures in the insides of the pump chambers 20 in the reciprocating pump devices 10A and 10B and that of the common discharge port 13 o side. The control device 3 performs the correcting operation which is described with reference to FIGS. 4( a)-4(h) or FIGS. 5( a)-5(h) on the basis of a monitoring result in the monitoring device when there is a difference in pressure between a pressure in the inside of the pump chamber 20 and the common discharge port side.

In this embodiment, as shown in FIG. 7, pressure sensors 14A and 14B for monitoring pressures in the respective insides of the pump chambers 20 in the reciprocating pump devices 10A and 10B are used as the monitoring device. In the monitoring device structured as described above, for example, at the time “t19”, a detection result of the pressure sensor 14B which is disposed in the pump chamber 20 in the reciprocating pump device 10B where a suction operation to the inside of the pump chamber 20 has been finished and a detection result of the pressure sensor 14A which is disposed in the pump chamber 20 in the reciprocating pump device 10A are compared with each other and a difference in pressure between the inside of the pump chamber 20 and the common discharge port side is monitored. This is because that, at the time “t14”, a detection result of the pressure sensor 14A in the reciprocating pump device 10A is equal to a pressure of the common discharge port side. The control device 3 determines on the basis of the monitoring result the condition where the correcting operation is performed during the time period “t19” through “t20”, in other words, which of the condition shown in FIGS. 4( a)-4(h) or the condition shown in FIGS. 5( a)-5(h) is performed. On the other hand, when there is no difference in pressure between the inside of the pump chamber 20 and the common discharge port side, the correcting operation is not performed.

(Specific Structural Example of Reciprocating Pump Device)

A specific structural example of the reciprocating pump devices 10A and 10B which are used in the metering pump device in this embodiment will be described with reference to FIGS. 3 and 8.

FIG. 8 is an exploded perspective view showing the reciprocating pump device which is longitudinally divided and is used in a metering pump device to which at least an embodiment of the present invention is applied. As shown in FIGS. 3 and 8, the main body portion 2 of the metering pump device 1 in this embodiment is structured so that the bottom plate 75, the base plate 76, the flow passage structuring plate 77 and the top plate 78 are laminated in this order. The reciprocating pump devices 10A and 10B are structured within holes formed in the base plate 76. In this embodiment, each of the reciprocating pump devices 10A and 10B include the pump chamber 20, the diaphragm valve 170 (valve element) for expanding and contracting an internal volume of the pump chamber 20 to perform suction and discharge of liquid, and the drive device 105 for driving the diaphragm valve 170.

The drive device 105 includes a ring-shaped stator 120, a rotation body 103 coaxially disposed on an inner side of the stator 120, a movable body 160 coaxially disposed on an inner side of the rotation body 103, and a conversion mechanism 140 for converting rotation of the rotation body 103 into a force for moving the movable body 160 in an axial direction to transmit to the movable body 160. In this embodiment, the drive device 105 is mounted between a foundation plate 79 and the base plate 76 in a space formed in the base plate 76.

In the drive device 105, the stator 120 is structured so that a unit including a coil 121 which is wound around a bobbin 123 and two pieces of yoke 125 which are disposed to cover the coil 121 is stacked in two layers in an axial direction. In this state, in both of the up-and-down two layers, pole teeth protruded in the axial direction from inner circumferential edges of two pieces of the yoke 125 are alternately juxtaposed in a circumferential direction to function as a stator of the stepping motor.

The rotation body 103 is provided with a cup-shaped member 130 which opens upward and a ring-shaped rotor magnet 150 which is fixed on an outer peripheral face of a cylindrical drum part 131 of the cup-shaped member 130. A center of a bottom wall 133 of the cup-shaped member 130 is formed with a recessed part 135 which is recessed upward in the axial direction. The foundation plate 79 is formed with a bearing part 751 which receives a ball 118 disposed in the recessed part 135. Further, an inside surface on an upper end side of the base plate 76 is formed with a ring-shaped stepped part 766 and an upper end portion of the cup-shaped member 130 is formed with a ring-shaped stepped part, which faces the ring-shaped stepped part 766 of the base plate 76, comprised of an upper end portion of the drum part 131 and the ring-shaped flange part 134. A bearing 180 comprised of a ring-shaped retainer 181 and bearing balls 182 which are held by the retainer 181 at separated positions in a circumferential direction is disposed in an annular space which is formed by these ring-shaped stepped parts. In this manner, the rotation body 103 is supported by the main body portion 2 in the state that the rotation body 103 is capable of rotating around an axial line.

An outer peripheral face of the rotor magnet 150 in the rotation body 103 faces the pole teeth which are juxtaposed in the circumferential direction along an inner peripheral face of the stator 120. In this embodiment, an “S”-pole and an “N”-pole are alternately arranged in the circumferential direction on the outer peripheral face of the rotor magnet 150, and the stator 120 and the cup-shaped member 130 structures the stepping motor.

The movable body 160 is provided with a bottom wall 161, a cylindrical part 163 which is protruded in the axial direction from a center of the bottom wall 161, and a drum part 165 which is formed in a cylindrical shape so as to surround the cylindrical part 163. A male screw 167 is formed on an outer periphery of the drum part 165.

In this embodiment, in order to structure the conversion mechanism 140 for reciprocatedly moving the movable body 160 in the axial direction by using rotation of the rotation body 103, a female screw 137 is formed on an inner peripheral face of the drum part 131 of the cup-shaped member 130 at four portions away from each other in the circumferential direction. In addition, the male screw 167 which is engaged with the female screw 137 in the cup-shaped member 130 to structure the power transmission mechanism 141 is formed on the outer peripheral face of the drum part 165 of the movable body 160. Therefore, when the movable body 160 is disposed on the inner side of the cup-shaped member 130 so as to make the male screw 167 engage with the female screw 137, the movable body 160 is supported on the inner side of the cup-shaped member 130. Further, the bottom wall 161 of the movable body 160 is formed with six elongated holes 169 as a through hole in the circumferential direction, and six projections 769 are extended from the base plate 76 so that lower end parts of the projections are 769 are fitted into the elongated holes 169 to structure a co-rotation preventive mechanism 149. In other words, when the cup-shaped member 130 is rotated, rotation of the movable body 160 is prevented by the co-rotation preventive mechanism 149 which is structured of the projections 769 and the elongated holes 169. Therefore, the rotation of the cup-shaped member 130 is transmitted to the movable body 160 through the power transmission mechanism 141 comprised of the female screw 137 and the male screw 167 of the movable body 160 and, as a result, the movable body 160 is linearly moved between one side and the other side in the axial direction depending on rotating direction of the rotation body 103.

The diaphragm valve 170 is directly connected with the movable body 160. The diaphragm valve 170 is formed in a cup shape which is provided with a bottom wall 171, a cylindrical drum part 173 which is formed upright in the axial direction from an outer peripheral edge of the bottom wall 171, and a flange part 175 which is widened on an outer peripheral side from an upper end of the drum part 173. A center portion of the bottom wall 171 is fixed with a fixing screw 178 and a cap 179 in a vertical direction in a state that the center portion of the bottom wall 171 is covered over the cylindrical part 163 of the movable body 160. Further, an outer peripheral edge of the flange part 175 of the diaphragm valve 170 is formed with a thick wall part functioning as a liquid-tightness and positioning portion. The thick wall part is fixed between the base plate 76 and the flow passage structuring plate 77 around the through hole 21 of the flow passage structuring plate 77. In this manner, the diaphragm 170 defines a bottom face of the pump chamber 20 and liquid-tightness between the base plate 76 and the flow passage structuring plate 77 is secured around the pump chamber 20.

In this state, the drum part 173 of the diaphragm valve 170 is turned around in a “U”-shape in cross section and a shape of a turn-around portion 172 varies depending on a position of the movable body 160. However, in this embodiment, the turn-around portion 172 of the diaphragm valve 170 which is formed in a “U”-shape in cross section is disposed in an annular space structured between a first wall face 168 formed of an outer peripheral face of the cylindrical part 163 of the movable body 160 and a second wall face 768 formed of inner peripheral faces of the projections 769 extended from the base plate 76. Therefore, the diaphragm valve 170 deforms to be developed or wound up along the first wall face 168 and the second wall face 768 under the state that the turn-around portion 172 is held in the annular space in every state.

Further, the bottom wall 133 of the cup-shaped member 130 is formed with one groove 136 over an angular range of 270° in the circumferential direction, and a bottom face of the movable body 160 is formed with a downward projection (not shown). In this embodiment, the movable body 160 does not rotate around the axial line but moves in the axial direction and, on the other hand, the rotation body 103 rotates around the axial line but does not move in the axial direction. Therefore, the projection and the groove 136 function as a stopper which determines a stop position of the rotation body 103 and the movable body 160. In other words, a depth of the groove 136 varies in the circumferential direction and, when the movable body 160 is moved downward in the axial direction, the projection is fitted into the groove 136 and the end part of the groove 136 is abutted with the projection by rotation of the rotation body 103. As a result, the rotation of the rotation body 103 is prevented and the stop position of the rotation body 103 with the movable body 160, i.e., the maximum expanded position of the internal volume of the diaphragm valve 170 is determined.

In the reciprocating pump devices 10A and 10B structured as described above, when the stepping motor in the drive device 105 is rotated in one direction, the diaphragm valve 170 is driven in the direction so that the internal volume of the pump chamber 20 is enlarged and, when the stepping motor is rotated in the other direction, the diaphragm valve 170 is driven in the direction so that the internal volume of the pump chamber 20 is reduced. In other words, when an electrical power is applied to the coil 121 of the stator 120, the cup-shaped member 130 is rotated and the rotation is transmitted to the movable body 160 through the conversion mechanism 140. Therefore, the movable body 160 performs a reciprocating linear-motion in the axial direction. As a result, the diaphragm valve 170 deforms in conformity to movement of the movable body 160 to expand or contract the internal volume of the pump chamber 20 and thus, in the pump chamber 20, inflow of liquid from the inflow passages 12Ai and 12Bi is performed and outflow of liquid to the outflow passages 12Ao and 12Bo is performed.

As described above, in the reciprocating pump devices 10A and 10B in accordance with this embodiment, rotation of the rotation body 103 by the stepping motor mechanism is transmitted to the movable body 160 through the conversion mechanism 140, in which the power transmission mechanism 141 comprised of the male screw 167 and the female screw 137 is utilized, to perform a reciprocating linear-motion in the movable body 160 to which the diaphragm valve 170 is fixed. Therefore, power is transmitted from the drive device 105 to the diaphragm valve 170 with the minimum necessary members and thus the size, thickness and cost of the reciprocating pump devices 10A and 10B can be reduced. Further, when lead angles of the male screw 167 and the female screw 137 in the power transmission mechanism 141 are set to be smaller or, when the number of the pole teeth of the stator on the driving side is increased, a minute feeding of the movable body 160 can be performed. Therefore, the volume of the pump chamber 20 can be controlled strictly and thus discharging in a fixed amount can be performed with a high degree of accuracy.

Further, in this embodiment, the diaphragm valve 170 is used and the turn-around portion 172 of the diaphragm valve 170 is deformed to develop or wind up along the first wall face 168 and the second wall face 768 under the state that the turn-around portion 172 is held in the annular space and thus excessive sliding does not occur. Therefore, a useless load does not occur and service life time of the diaphragm valve 170 becomes longer. Further, the diaphragm valve 170 does not deform even when a pressure is applied by liquid in the pump chamber 20. Therefore, according to the reciprocating pump devices 10A and 10B in this embodiment, discharging with a fixed amount can be performed with a high degree of accuracy and reliability is also high.

In addition, the rotation body 103 is rotatably supported around the axial line by the main body portion 2 through the bearing balls 182. Therefore, sliding loss is small and, since the rotation body 103 is stably held in the axial direction, a thrust force in the axial direction is stable. Accordingly, the size of the drive device 105 can be reduced and improvement of the durability and discharging performance can be obtained.

In this embodiment, a screw is utilized for the power transmission mechanism 141 of the conversion mechanism 140 but a cam groove may be utilized. In addition, in the embodiment described above, a cup-shaped diaphragm valve is used as a valve element. However, a diaphragm valve having another shape or a piston provided with an O-ring may be used.

[Specific Structural Example of Active Valve]

With reference to FIG. 3 and FIG. 9, in a metering pump device in this embodiment, a specific structural example of the active valve will be described below which is used as the inflow side valves 11Ai and 11Bi and the outflow side valves 11Ao and 11Bo. FIG. 9 is an explanatory longitudinal sectional view showing an active valve which is used as the inflow side valves 11Ai and 11Bi and the outflow side valves 11Ao and 11Bo in the metering pump device 1 to which at least an embodiment of the present invention is applied.

In FIG. 3 and FIG. 9, the active valve is provided with a stepping motor 301 that is a drive source, an inflow port 308 a and an outflow port 308 b. A lead screw 302 comprised of, for example, a right-hand screw is press-fitted and fixed to the rotation shaft 301 a of the stepping motor 301. The lead screw 302 rotates in a direction which is the same as that of the stepping motor 301. A female screw 303 a of the valve holding member 303 is threadedly fitted to the lead screw 302. Therefore, when the stepping motor 301 is rotated in a CCW direction (counterclockwise direction) which is viewed from the lead screw 302 side, the valve holding member 303 approaches to the stepping motor 301 and, when the stepping motor 301 is rotated in a CW direction (clockwise direction) which is viewed from the lead screw 302 side, the valve holding member 303 goes away from the stepping motor 301. In other words, rotation of the lead screw 302 is converted into a linear-motion because the lead screw 302 and the valve holding member 303 are engaged with each other through screw engagement and turning of the valve holding member 303 is prevented.

A spring receiving part 303 b is concentrically formed on an outer peripheral side of the valve holding member 303 and a spring 304 is held by the spring receiving part 303 b and the stepping motor 301. The spring 304 is comprised of a compression coil spring, which urges the valve holding member 303 in a direction separating from the stepping motor 301. In this embodiment, a compression coil spring is utilized but, for example, a tension coil spring may be utilized. In this case, a tension coil spring is held on an opposite face of the spring receiving part 303 b of the valve holding member 303.

A center portion of the valve holding member 303 is formed with a convex-shaped diaphragm holding part 303 c, which is fitted to an undercut part 260 a of the diaphragm valve 260. In this embodiment, the diaphragm valve 260 is fixed by means of that its outer peripheral portion 260 b is pinched by the base plate 76 and the flow passage structuring plate 77 and a bead 260 e on its outer peripheral side is also pinched and fixed. The bead 260 e prevents fluid from leaking from a gap space between the base plate 76 and the flow passage structuring plate 77 to improve sealing property. Further, since a film part 260 c of the diaphragm valve 260 is easily deformed, the film part 260 c is formed in a circular arc shape so that stress is not concentrated. In this embodiment, the diaphragm valve 260 is formed with a bead part 260 d in a concentric manner on an opposite side to the undercut part 260 a and on an abutting portion with the flow passage structuring plate 77.

In the active valve structured as described above, the valve holding member 303 is urged in a direction separating from the stepping motor 301 by the spring 304. Therefore, when the valve holding member 303 is linearly moved, a state is maintained in which a slant face on the stepping motor 301 side of the screw part of the lead screw 302 is contacted with a slant face on an opposite side to the stepping motor 301 side of the female screw 303 a of the valve holding member 303. In other words, a state that the lead screw 302 and the valve holding member 303 are engaged with each other is maintained. On the other hand, when the hole 277 is closed by the diaphragm valve 260, the urging force of the spring 304 is balanced with a force of counteraction which is applied to the diaphragm valve 260 by the flow passage structuring plate 77, and a state is maintained in which a slant face, which is on an opposite side of the stepping motor 301 side, of the screw part of the lead screw 202 is not contacted with a slant face on the stepping motor 301 side of the female screw 303 a of the valve holding member 303. In other words, the lead screw 302 and the valve holding member 303 are maintained in a non-engaging state with each other through a play (backlash), and the diaphragm valve 260 is urged by the spring 304 in a direction closing the hole 277. Therefore, the hole 277 can be closed securely.

[Another Specific Structural Example of Active Valve]

With reference to FIGS. 3 and 10, in a metering pump device in this embodiment, another specific structural example of an active valve which is used as inflow side valves 11Ai and 11Bi and outflow side valves 11Ao and 11Bo will be described below.

FIG. 10 is an explanatory longitudinal sectional view showing an active valve which is used as inflow side valves 11Ai and 11Bi and outflow side valves 11Ao and 11Bo in the metering pump device 1 to which at least an embodiment of the present invention is applied and which is viewed from obliquely below. As shown in FIGS. 3 and 10, an active valve which is used as the inflow side valves 11Ai and 11Bi and the outflow side valves 11Ao and 11Bo is provided with a linear actuator 201 within a hole 765 of the base plate 76. The linear actuator 201 includes a cylindrical fixed body 203 and a roughly cylindrical movable body 205 which is disposed on an inner side of the fixed body 203. The fixed body 203 is provided with a coil 233 circumferentially wound around a bobbin 231, and a fixed body side yoke 235 which surrounds the coil 233 from an outer peripheral face of the coil 233 to an inner side through both sides in an axial direction of the coil 233 and whose one tip end part 236 a and the other tip end part 236 b are faced each other in the axial direction on an inner peripheral side of the coil 233 through a slit 237. The movable body 205 includes a first movable body side yoke 251 formed in a circular plate shape and a pair of magnets 253 a and 253 b which are laminated on both sides in the axial direction of the first movable body side yoke 251. Rare earth magnet of Nd—Fe—B system or Sm—Co system, or resin magnet may be used for the pair of the magnets 253 a and 253 b. Further, in the movable body 205, second movable body side yokes 255 a and 255 b are respectively laminated on end faces on an opposite side to the first movable body side yoke 251 of the pair of the magnets 253 a and 253 b.

Each of the pair of the magnets 253 a and 253 b is magnetized in the axial direction, and the same poles are directed to the first movable body side yoke 251. In this embodiment, each of the pair of the magnets 253 a and 253 b is disposed so that an “N”-pole is directed to the first movable body side yoke 251 and an “S”-pole is directed to an outer side in the axial direction. However, the magnetizing direction may be reversed.

In this embodiment, the outer peripheral face of the first movable body side yoke 251 is protruded on an outer peripheral side from the outer peripheral faces of the pair of the magnets 253 a and 253 b. Further, the outer peripheral faces of the second movable body side yokes 255 a and 255 b are protruded on an outer peripheral side from the outer peripheral faces of the pair of the magnets 253 a and 253 b.

Recessed parts are formed on both end faces in the axial direction of the first movable body side yoke 251, and the pair of the magnets 253 a and 253 b are respectively fitted to the recessed parts and fixed with an adhesive or the like. The first movable body side yoke 251, the pair of the magnets 253 a and 253 b and the second movable body side yokes 255 a and 255 b may be fixed to each other by adhesion, press fitting or their combination to be integrated.

Further, bearing plates 271 a and 271 b (bearing member) are fixed to opening parts on both sides in the axial direction of the fixed body 203. Support shafts 257 a and 257 b which are projected on both sides in the axial direction from the second movable body side yokes 255 a and 255 b are slidably inserted into the holes of the bearing plates 271 a and 271 b. In this manner, the movable body 205 is supported by the fixed body 203 in the state that it is capable of reciprocating in the axial direction. In this state, the outer peripheral face of the movable body 205 faces the inner peripheral face of the fixed body 203 through a predetermined gap space, and the tip end parts 236 a and 236 b of the fixed body side yoke 235 face each other in the axial direction in a gap space between the outer peripheral face of the first movable body side yoke 251 and the inner peripheral face of the coil 233. Further, a space is secured between the movable body 205 and the fixed body side yoke 235. The second movable body side yokes 255 a and 255 b and the support shafts 257 a and 257 b may be fixed by adhesion, press fitting or their combination to be integrated.

In the linear actuator 201 structured as described above, in this embodiment, a shaft body 259 is connected with a tip end part the support shaft 257 b, and a center portion of the diaphragm valve 260 disposed in a valve chamber 270 is connected with the shaft body 259. A ring-shaped thick wall part 261 which functions as liquid-tightness and positioning is formed on an outer peripheral side of the diaphragm valve 260. The outer peripheral side including the ring-shaped thick wall part 261 of the diaphragm valve 260 is sandwiched between the base plate 76 and the flow passage structuring plate 77 to secure liquid-tightness.

In the linear actuator 201 structured as described above, during a period when an electric current flows through the coil 233 from a rear side to a front side on the right side in the paper and, the electric current flows through the coil 33 from the front side to the rear side on the left side in the paper, the movable body 205 is received with a thrust force in the axial direction by a Lorentz force as shown by the arrow “B” to be moved. As a result, a hole 277 structuring a middle portion of the flow passage is closed and the flow passage is shut off. On the other hand, when the energization direction to the coil 233 is reversed, the movable body 205 is moved downward along the axial direction as shown by the arrow “A” to open the hole 277 structuring the middle portion of the flow passage.

In the linear actuator 201 in this embodiment, the movable body 205 is advanced by a magnetic force and, in addition, a coil spring 291 in a truncated-cone shape is disposed between the bearing plate 271 a and the second movable body side yoke 255 a as an urging member on one side in the axial direction. Therefore, when the movable body 205 is moved down, the movable body 205 is moved while the compression spring is deformed and, when the movable body 205 is moved upward, a returning force of the compression spring to its original shape assists to move it at a high speed.

In this embodiment, the valve element is not limited to the diaphragm valve 260 and a bellows valve or another valve element may be used. Further, the support shafts 257 a and 257 b and the valve element may be structured of separated members which are to be integrated, or one piece of member may be used which is integrally structured of the support shafts 257 a and 257 b and the valve element.

As described above, in this embodiment, the pair of the magnets 253 a and 253 b in the movable body 205 is disposed so that the same pole are faced each other and thus magnetic repulsive forces are acted on each other. However, since the first movable body side yoke 251 is disposed between the magnets 253 a and 253 b, the pair of the magnets 253 a and 253 b can be fixed in the state that the same poles are directed to each other.

Further, the pair of the magnets 253 a and 253 b in the movable body 205 is disposed so that the same poles are directed to the first movable body side yoke 251. Therefore, a strong magnetic flux is generated from the first movable body side yoke 251 in the radial direction. As a result, when the first movable body side yoke 251 and the peripheral face of the coil 233 are faced each other, a large thrust force can be applied to the movable body 205.

In addition, magnetizing is performed on the magnets 253 a and 253 b in the axial direction and thus, different from a case that magnetizing is performed on the magnets 253 a and 253 b in the radial direction, the magnetizing is easy even when they are miniaturized and suitable for mass production.

Moreover, in this embodiment, the outer peripheral face of the first movable body side yoke 251 is protruded on the outer peripheral side from the outer peripheral faces of the pair of the magnets 253 a and 253 b. Therefore, even when the fixed body side yoke 235 is provided, a magnetic attractive force acting on the movable body 205 in the direction perpendicular to the axial direction can be made smaller. Similarly, the outer peripheral faces of the second movable body side yokes 255 a and 255 b are protruded on the outer peripheral side from the outer peripheral faces of the pair of the magnets 253 a and 253 b. Therefore, even when the fixed body side yoke 235 is provided, magnetic attractive forces acting on the movable body 205 in the direction perpendicular to the axial direction can be made smaller. As a result, assembling work is easily performed and the movable body 205 is hardly inclined.

Further, in this embodiment, the magnets 253 a and 253 b are disposed on the inner peripheral side of the coil 33 and thus, in comparison with a case that the magnets 253 a and 253 b are disposed on the outer side of the coil 233, the magnets 253 a and 253 b can be made smaller and the active valve can be structured at a low cost. Further, since the coil 233 is disposed on the outer side, a magnetic path can be closed only with the fixed side yoke.

In addition, the bearing plates 271 a and 271 b which movably support the support shafts 257 a and 257 b in the axial direction are held by the opening parts in the fixed body 203 which open in the axial direction. Therefore, bearing members are not required to be disposed separately. Further, since the bearing plates 271 a and 271 b can be fixed with the fixed body 203 as a reference, the support shafts 257 a and 257 b are not inclined.

[Application of Metering Pump Device]

The metering pump device 1 to which at least an embodiment of the present invention is applied is used, for example, to quantitatively supply water to a reformer of various fuel cells. Further, the metering pump device 1 to which at least an embodiment of the present invention is applied may be used for quantitatively supplying urea aqueous solution to a reformer for resolving and removing nitrogen oxides from exhaust gas of a diesel engine or used for feeding infusion liquid. Especially, the metering pump device 1 is suitable to discharge at a constant rate or quantitatively in a field where a difference in pressure is large between a suction side and a discharge side.

Anther Embodiment

In the embodiment described above, two reciprocating pump devices 10A and 10B are used. However, at least an embodiment of the present invention may be applied to a metering pump device which is provided with three or more reciprocating pump devices.

While the description above refers to particular embodiments of the present invention, it will be understood that many modifications may be made without departing from the spirit thereof The accompanying claims are intended to cover such modifications as would fall within the true scope and spirit of the present invention.

The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims, rather than the foregoing description, and all charges which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. 

1. A metering pump device comprising: a plurality of reciprocating pump devices each of which is connected with an inflow side valve and an outflow side valve on an inflow side and an outflow side; a common discharge port which is connected with the plurality of the reciprocating pump devices through the outflow side valves; and a control part for controlling the inflow side valves, the outflow side valves and the reciprocating pump devices; wherein the control part sets a discharge period and a waiting period for each of the plurality of the reciprocating pump devices so as to shift timings of the discharge period and the waiting period, and a starting time and an ending time of the discharge period of one of the reciprocating pump devices are superposed on an ending time and a starting time of the discharge period of another reciprocating pump device and, after a suction operation into a pump chamber has been performed in the waiting period and before the discharge period, a correcting operation is performed in which both of the inflow side valve and the outflow side valve are closed and a volume within the pump chamber is expanded or contracted to eliminate a difference in pressure between a pressure within the pump chamber and a common discharge port side.
 2. The metering pump device according to claim 1, further comprising a common suction port which is connected with the plurality of the reciprocating pump devices through the inflow side valves.
 3. The metering pump device according to claim 2, wherein a drive source for the reciprocating pump device is a stepping motor.
 4. The metering pump device according to claim 3, wherein a variation amount of an internal volume of the pump chamber corresponding to one (1) step of the stepping motor is set to be 1/100 or less with respect to an entire internal volume of the pump chamber.
 5. The metering pump device according to claim 3, further comprising a monitoring device for directly or indirectly monitoring a difference in pressure between a pressure in an inside of the pump chamber in the reciprocating pump device and a pressure on the common discharge port side, wherein the control part performs the correcting operation on a basis of a monitoring result in the monitoring device when a difference in pressure exists between the pressure in the inside of the pump chamber and the pressure on the common discharge port side.
 6. The metering pump device according to claim 5, wherein the monitoring device comprises: a plurality of first pressure sensors for monitoring respective pressures within the pump chambers of the plurality of the reciprocating pump devices, and a second pressure sensor for monitoring a-the pressure on the common discharge port side, wherein the difference in pressure is monitored by comparing a detection result of the first pressure sensor with a detection result of the second pressure sensor.
 7. The metering pump device according to claim 5, wherein the monitoring device comprises a plurality of pressure sensors for monitoring respective pressures within the pump chambers of the plurality of the reciprocating pump devices, and the difference in pressure is monitored by comparing a detection result of a pressure sensor, which is disposed in the pump chamber of the reciprocating pump device in which the suction operation has been performed, with a detection result of a pressure sensor which is disposed in the pump chamber of the reciprocating pump device whose output side valve is opened.
 8. The metering pump device according to claim 3, wherein a number of the reciprocating pump device is two, and a control device sets an expanding speed of the pump chamber when the suction operation is performed higher than a contracting speed of the pump chamber in the discharge period.
 9. The metering pump device according to claim 1, wherein the reciprocating pump device is provided with a drive source which is one of a stepping motor and an AC synchronous motor.
 10. The metering pump device according to claim 1, wherein a drive source for the reciprocating pump device is a stepping motor, and a variation amount of an internal volume of the pump chamber corresponding to one (1) step of the stepping motor is set to be 1/100 or less with respect to an entire internal volume of the pump chamber.
 11. The metering pump device according to claim 1, further comprising a monitoring device for directly or indirectly monitoring a difference in pressure between a pressure in an inside of the pump chamber in the reciprocating pump device and a pressure on the common discharge port side, wherein the control part performs the correcting operation on a basis of a monitoring result in the monitoring device when a difference in pressure exists between the pressure in the inside of the pump chamber and the pressure on the common discharge port side.
 12. The metering pump device according to claim 11, wherein the monitoring device comprises: a plurality of first pressure sensors for monitoring respective pressures within the pump chambers of the plurality of the reciprocating pump devices, and a second pressure sensor for monitoring the pressure on the common discharge port side, wherein the difference in pressure is monitored by comparing a detection result of the first pressure sensor with a detection result of the second pressure sensor.
 13. The metering pump device according to claim 11, wherein the monitoring device comprises a plurality of pressure sensors for monitoring respective pressures within the pump chambers of the plurality of the reciprocating pump devices, and the difference in pressure is monitored by comparing a detection result of a pressure sensor, which is disposed in the pump chamber of the reciprocating pump device in which the suction operation has been performed, with a detection result of a pressure sensor which is disposed in the pump chamber of the reciprocating pump device whose output side valve is opened.
 14. The metering pump device according to claim 1, wherein a number of the reciprocating pump device is two, and the control device sets an expanding speed of the pump chamber when the suction operation is performed higher than a contracting speed of the pump chamber in the discharge period.
 15. A metering pump device comprising: a plurality of reciprocating pump devices each of which is connected with an inflow side valve and an outflow side valve on an inflow side and an outflow side; a common discharge port which is connected with the plurality of the reciprocating pump devices through the outflow side valves; and pressure sensors for monitoring respective pressures within a pump chamber of the plurality of the reciprocating pump devices.
 16. The metering pump device according to claim 15, further comprising a common suction port which is connected with the plurality of the reciprocating pump devices through the inflow side valves.
 17. The metering pump device according to claim 16, wherein the reciprocating pump device is provided with a drive source which is one of a stepping motor and an AC synchronous motor. 